Dialdehydes special

Macrocycles have been prepared by formation of macrocyclic imines as well as by using variations of the Williamson ether synthesis ". Typically, a diamine or dialdehyde is treated with its counterpart to yield the Schiff s base. The saturated macrocycle may then be obtained by simple reduction, using sodium borohydride, for example. The cyclization may be metal-ion templated. In the special case of the all-nitrogen macrd-cycle, 15, the condensation of diamine with glyoxal shown in Eq. (4.14), was unsuccess-ful ... 

Dialdehyde starch,176-178 block reactive starch179 and cationic aldehyde starch180 181 comprise a special class of starches that can react with cellulose through the formation of covalent hemiacetal or acetal bonds. The zwitterion group is another functional group that has been utilized in conjunction with cationic and acetal groups. 

In view of the great facility with which base-catalyzed alkoxylations of nitro-olefinic sugars tend to occur, it might be suspected that side reactions involving the formation of methylated derivatives might accompany nitromethane cyclizations of sugar dialdehydes in methanolic medium. There is as yet no evidence for this, but special... 

We also examined aldol condensations of the dialdehyde 17. Without the special catalysis afforded by the cyclodextrin i w-imidazoles there was an almost random reaction to form compounds 18 and 19, as either aldehyde acted as the enofizing group. However, the cyclodextrin imidazole catalysts directed the selective formation of products 19, with no selectivity among its stereoisomers. Interestingly, the least selective catalyst for 17 was the cyclodextrin mono-imidazole, the AD isomer of the fcw-imidazole was more selective, and the most selective was the AB isomer. Obviously these results indicate that the cyclodextrin imidazole catalysts promote enolization of the aldehyde group closest to the cyclodextrin, as expected, but the subtlety of preferences among the bw-imidazole isomers is not yet understood in this case. 

A special type of deterrent effect was shown by Ma (1977b). A sesquiterpene dialdehyde isolated from the warburgia plant blocks the sugar receptor cell of S. exempta for 10-20 min after two contacts of 3 min. This inhibitory effect on the sensory neuron has been correlated with a suppression of the feeding response to sucrose. Similarly, Kennedy and Halpern (1980) showed that ziziphin, a cyclic peptide alkaloid of Rhamnaceae, also temporarily inhibits the fly sugar (but not the salt) receptor. 

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